It is known that vascular bubbles and tissue gas can form in divers using currently-accepted diving schedules and that undesirable hematological sequelae result from these non-symptomatic bubbles. This indicates a need for more precise definition of critical conditions in vivo required for both phase separation and resulting sequelae, so that decompression procedures can avoid bubbles rather than bends. These conditions can more efficiently be determined in fish due to their unique physiology--freedom from the thermal problems found in air breathers, suitability for being subjected to changes in hydrostatic and gas pressures independently, and the basic similarity in their response to supersaturation stress. The interrelationships of bubble formation and hematological sequelae can then be investigated through combined experiments monitoring bubble formation and changes in coagulation function in the same fish. This will identify hematological changes which can be used as sensitive indicators of decompression stress from precisely defined supersaturations. Such information will facilitate more realistic decompression procedures and more effective treatment of decompression sickness.